The invention relates to a method and an arrangement for splicing optical waveguides and, more specifically, for effecting such splicing under field conditions i.e. directly in cable pits where the waveguides requiring splicing are housed.
It is known to splice optical waveguides, such as optical fibres, by means of automatic welding. However, automatic welding requires a high temperature, approximately 2000.degree. C., and a clean environment. The welding must, therefore, be carried out in an enclosed environment, such as a special caravan which is transported to the site where the optical fibres requiring splicing are located. It is a requirement of such an arrangement that the optical fibres which are usually housed in a cable pit in the ground, have sufficiently long loops so that they can be drawn into the caravan for splicing. Even though a good splice is obtained with this arrangement, the technology is expensive because of the need to use special equipment. Furthermore, it is not always possible to transport the special caravan to all possible locations where the splicing of optical fibres needs to be effected.
Purely mechanical splices have also already been used, that is to say, the ends of the two optical fibres requiring splicing are enclosed within a capsule and placed against one another with an air gap therebetween. This arrangement can cause losses in the splice because in cutting the ends of the fibres in readiness for splicing, the cut surfaces at the ends of the fibres are not quite perfect and this creates reflection and attenuation with each change in the refractive index at the splice. It is known to alleviate these problems by filling the air gap with refractive index-matching means, for example, silicon oils or epoxy cements. With silicon oils which are free flowing, leakage can occur. Moreover, the silicon oils and the optical fibre waveguides have different temperature characteristics. There are also problems with different ageing characteristics. The use of epoxy cements for splicing optical waveguides which give rise to similar problems to the ones outlined above for silicon oils, can be a health hazard in that they emit vapours that can be damaging to health.
It is an object of the present invention to overcome the foregoing problems with known splicing arrangements by the provision of a method and an arrangement for splicing optical waveguides, such as optical fibres, that can be effected in the field, for example, in the cable pits in which the waveguides are housed and that produces splices which have good refractive index matching and thereby relatively low losses and which have optical, ageing and temperature characteristics similar to those of the optical waveguides.